Carhart-Harris et al. 2016 – Psychological effects of LSD


Carhart-Harris et al. 2016 gave LSD to 20 healthy-typed participants who had previously had a psychedelic experience.

Then they slid the participants into an MRI scanner and imaged their brains. Two weeks later, the participants filled out a bunch of surveys about their psychology.

Actually Carhart-Harris did something cleverer than that – they slid each participant into the MRI machine twice: once after injecting them with LSD, and once after injecting them with a placebo.

As you probably expect, the LSD-injected MRI scans were very different from the placebo-injected MRI scans (examples in this other 2016 Carhart-Harris et al. paper... the man authors a lot of papers).

But that's not very surprising. Of course a person's brain activity looks different while tripping!

For our purposes, Carhart-Harris 2016 is interesting because of the stuff it found in its psychological surveys:

The LOT-R was chosen as it is a well-validated measure of trait or dispositional optimism (Scheier et al. 1994), the NEO PI-R [NEO Personality Inventory] was chosen as it is well-validated and previous research has shown its sensitivity to the enduring effects of psychedelics (MacLean et al. 2011), and the PDI [Peters’ Delusions Inventory] was chosen as it is a well-validated measure of delusional thinking that has shown to be sensitive to psychotic-like symptoms in the general population (Peters et al. 1999).

Carhart-Harris found:

Optimism was significantly increased 2 weeks after LSD (t=2.91, df=18, p=0.005, Cohen’s d=0.56), as was trait Openness (t=1.95, df=19, p=0.03, Cohen’s d = 0.16) (Fig. 3), and there were no such changes in optimism or personality post-placebo.

Recall that Openness is one of the Big-Five psychological traits, which are tracked by the NEO PI-R.

Implicit here is that the other 4 Big-Five traits did not change after the LSD trip.

Here's a chart of the result:


Oh, and they also found that participants weren't more delusional two weeks after LSD than two weeks after placebo, even though the LSD trip itself does resemble psychosis.

So we can take Carhart-Harris as some evidence that an LSD trip will make most healthy-typed people more optimistic and more Open, two weeks later.

It gets bonus points for being placebo-controlled; most psychedelic studies to date have been open-label (i.e. no placebo).

A few limitations to this study: